Preparation Of Nitrogen-Doped Reduced Graphene Oxides Nanocomposites For Electrochemical Oxygen Reduction

This thesis is mainly composed of the following three sections:Firstly, graphene oxide (GO) was prepared by the modified Hummers method, using nature graphite as raw material, concentrated sulfuric acid as inserted layer agent and potassium permanganate as strong oxidizing agents. The as-prepared GO was characterized with scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractomer (XRD), fourier transform infrared spectrometer (FTIR), ultraviolet ray (UV) and thermogravimetric analysis (TGA). The results showed that the translucent GO nanosheets contain abundant functional groups (-OH,-COOH,-C-O-C-) with edge defect, which can be highly dispersed in the aqueous solution.Secondly, a simple hydrothermal method for preparing nitrogen-doped reduced graphene oxide/a-Fe2O3 nanodiscs nanocomposites (NG/a-Fe2O3) was demonstrated. Potassium ferricyanide (K3[Fe(CN)6]) was used as precursor. The formation of NG/a-Fe2O3 was confirmed by SEM, TEM, XRD, energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), raman spectra (Raman), FTIR and TGA. The results indicated that the thin single-crystal a-Fe2O3 nanodiscs are grown on the well dispersed reduced graphene oxides successfully. Nitrogen content in NG/a-Fe2O3is6.13at%.The catalytic performance of NG/a-Fe2O3 for oxygen reduction reaction (ORR) was tested through the electrochemical method of cyclic votammetry (CV), linear sweep voltammetric (LSV) and i-t curve. Under the optimized experimental conditions of 10.0 mL 1.5 mg·mL-1 K3[Fe(CN)6] and 10.0 mL 1.0 mg9mL-1 GO, the fabricated NG/α-Fe203 material showed good catalytic activity with a peak voltage of-0.201 V, a peak current density of 62.00μA·cm-2 and better methanol resistance than the commercial 20% Pt/C.Thirdly, nitrogen-doped reduced graphene oxides/cobalt oxides (NG/CO3O4) nanocomposites were prepared through hydrothermal method with GO, cobalt chloride (CoCl2·6H2O) and ammonia (NH3·H2O). The NG/Co3O4 was characterized with SEM, TEM, XRD, EDS, XPS, Raman, FTIR and TGA. The results confirmed that nitrogen-doping were effectuated successfully with a doping amount of 10.43 at% and the thin single-crystal Co3O4 are grown on the well dispersed reduced graphene oxides successfully.NG/Co3O4 was used as electrochemical catalyst for ORR and its electrocatalytic performances were tested by CV, LSV and i-t. When the concentration of GO is 1.5 mg·mL-1 (10.0 mL), CoCl2 is 2.0 mg·mL-1 (5.0 mL) and the addition of NH3H2O is 8.0 mL, NG/Co3O4 showed a rather good catalytic performance with a peak voltage of-0.163 V, a peak current density of 73.01 μA·cm-2 and better methanol resistance than the commercial 20% Pt/C.